Helicase Motif III in SecA is essential for coupling preprotein binding to translocation ATPase

被引:23
作者
Papanikou, E
Karamanou, S
Baud, C
Sianidis, G
Frank, M
Economou, A
机构
[1] Fdn Res & Technol Hellas, Inst Mol Biol & Biotechnol, GR-71110 Iraklion, Crete, Greece
[2] Univ Crete, Dept Biol, GR-71110 Iraklion, Crete, Greece
关键词
SecA; ATPase; DNA/RNA helicase; protein translocation; signal peptide;
D O I
10.1038/sj.embor.7400206
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The SecA ATPase is a protein translocase motor and a superfamily 2 (SF2) RNA helicase. The ATPase catalytic core ('DEAD motor') contains the seven conserved SF2 motifs. Here, we demonstrate that Motif III is essential for SecA-mediated protein translocation and viability. SecA Motif III mutants can bind ligands ( nucleotide, the SecYEG translocase 'channel', signal and mature preprotein domains), can catalyse basal and SecYEG-stimulated ATP hydrolysis and can be activated for catalysis. However, Motif III mutation specifically blocks the preprotein-stimulated 'translocation ATPase' at a step of the reaction pathway that lies downstream of ligand binding. A functional Motif III is required for optimal ligand-driven conformational changes and kinetic parameters that underlie optimal preprotein-modulated nucleotide cycling at the SecA DEAD motor. We propose that helicase Motif III couples preprotein binding to the SecA translocation ATPase and that catalytic activation of SF2 enzymes through Motif-III-mediated action is essential for both polypeptide and nucleic-acid substrates.
引用
收藏
页码:807 / 811
页数:5
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